The Non Patent Literature 1 listed below is a literature in which technical specifications related to a vehicle transmission system in a train are described.
Non Patent Literature 1 is a specification defining backbone transmission of an Ethernet® system for connecting vehicle formations, in order to realize interconnection between the vehicle formations of different manufacturers' vehicles. In this literature, as a technique of improving the reliability of the communication apparatus (ETBN: Ethernet® Train Backbone Node) that performs data communication between fixed formations, redundancy of ETBNs is described.
Also in Non Patent Literature 1, as a method for realizing redundancy of ETBNs, there is a description suggesting using the IETF (Internet Engineering Task Force) RFC (Request For Comments) 5798 VRRP (Virtual Router Redundancy Protocol).
When an ETBN is made redundant in accordance with the VRRP, an ETBN (ETBN Master) that operates as a master periodically transmits a frame for alive monitoring (VRRP Advertisement). Meanwhile, another ETBN (ETBN Backup) that operates as a backup determines that the ETBN operating as a master has malfunctioned if the ETBN Backup does not receive any frame for alive monitoring (hereinafter, “alive monitoring frame”) for a predetermined time period, and the ETBN Backup itself becomes a master and starts to operate as a master.
For example, in Patent Literature 1, an invention is described that causes network devices to be redundant in accordance with the VRRP.